Pulse repeating system



PULSE REPEATING SYSTEM Filed July 10, 1943 Hun-mm UH LI "1 FROM CALLINGEND AN SWER/NG r fffgg l FROM CALLED END FROM CALLED END lNVENTO/P yR.B.$HANCK A T ram/Er Patented Jan. 9, 1945 wu NI'TIED a OFFTCE i v Q lcheeses;

,PULSE REPEATI NG ,SYST-EM .Roy B. Shanek; Douglas Manpfi-N. t Yassignor to 4 Bell "Telephone Laboratories, Incorporated, L NewXorkN.T1Y., a corporation of-Nemilork pp i n ,lulylfl, 9 Seria No $194,210

2 Claims. (C L 179-849 The invention relates: to pulse-repeating,systerns and more particularly: towsystems ot this type operating lamaduplex; basis.

It is an object o-L'theiinvention, toiprovidea pulse repeating systemwitha simplified-duplex balance and capable of; efifioient-loperationunder conditions. of line variations :and int erenc It is a n more.specific obiecti of 1 the inventione provide; aesystemiof th s: ype=WhiGhsW th etandardized equipmentnis adapted: iorirepe nauseheating andsupervisin p lses hi0 tcl p. one

switching .systemstover: lines; of a greatly rod fielrincharacteristicsiandi lengths.

The" selective; supervisory "operations; ot automatic telephoneswitching systems are frequently performed over extensive line circuitswsuchoas to11i1ines, the ilengths ofimhichsdiffengre tlyand which aresubject to iwellaknown disturbances and interferences.Thezselectingvzpulses; usually I termed the: t dial pulses, i areusually transmitted tions in the "line circuit :The reason for duplexinthe ipulsercircuitzis.mainlyLto betfound in the fact that thewtraflic'requirements include;;.the transmission :in: both directions overthetlineyoircuit of supervisory signals cit-pulses. (The; opera.- tionsare complicated ,by the: [requirement that, in the series of operationsinvolved inhthe setting up of a connection, thedinelcircuit is placed under two different conditions, which .;may :1b8

termed the idle andthe busy conditions. The pulse repeating system isadaptedntooreceive dialing pulses from a calling. station, "which maybea remotetelephone:subsoribers station or a local operatorsj dialinglcircuit, andoto :ree

peat the .pulses oven an outgoing Aline circuit. to

a i distant telephone exchange, equipped :fOEf automatic switching in:response: to; the zdial; pulses for the selection of; another exchange.101' another subscriberfswstation. i

Th r p ating,circuiteincludes antler-chan ing relay for applying twodifferent transmitting potentials to the line circuit: correspondingtoe-the two iconditionsrrofx jtheypuiscs, 4name1y,;:;markin and: spacinor current; andono current. Jlfhe n s:fromtheipcletchan in -rclyarevimpresse upon. a duplex; circuit includingmthelaliney tcir cuit in;one branchmand 2R3; .xbalancingo circuityim he other branch. v v v v 1 Apolar receiving re eyqisi ludedinthdd @plex circuit for receptionoftsignals bincoming te c fi 'o thisp r sethe n l tc eyime v v y outeoneisignals when: hci npe a c balanc be connec ed-i ets!well-knew mennetes J93 avin it npe ati e .minfine d re l p-in llwie i 1 36 tw bal ncedi circuits on ecte i in a rid e e w enthee -c m te ma cod n Mth 1 miesnco rbiifl s 1 iijafs :eitim t arteietrcd t t i wo de t revent th eceiyne. cla mm. IQSP liQ j to the .onteoineinu eess na ar ixm 20 wcl ncwn pact tem l .lheevetem tele rap rep atin sy ae t e -cq pulses 1 o i aprede r ned;\fre ue cy. ,usuelly w rei n r esed upon the duplex circuitby oper h lthcttoebe in cespressed ;.Qnn unb ance ev t m u balance urtai-tear h pnera mth z eceivin e :Sii lQH lHllJP XE i ui unha an edi nd thes on e curejv ote el ten l to i th re a equalaand a equalizin or yunwindineltateai balance current will flow through thetvindings andoperate the rela rdize t-to supp a b an e-Iona lar e, var

ri tymo i ine' ci qu tsvso hat it m ib m m it .tacture :35

ance ti t e nventiqn.th teystemni t-the mc ane tsdthet i w t b iunnecessr t adjust theha anc n networ i comp n a e to i tcircuit du i in ludintemper ture; and-leakag chan es he in ese nday swereldemands i naccuracy- E lihQ-DWFPQ u ou i ed: he: en io ro ide a arran ment lfor pentin t al L 1 ve1 ation wh c wou be. du tt iz mnr p v ,5 :s cnscsb there e vin -relay tdurinlejithe tran mission;ofoutgoing pulsesresultingfrom unbalance. cond tionsi-B th ip o is n a ve sign of ba an n tworJmaytbei ased on" ce tain average or predominantlhne conditions even the:line circuita thisrreiay; beingvzunatfiected J15 among the largevariety; pftcpnditions ,met with on c the, P le the two operatin windinstwil e he rela n-t r d e dunec ot anceiwit efeat r lithevent on, thebal nc n ne w kjri implified en e e i omn zat t ly o rcc t- Jim-a corsimplification ot the ba ancin -ne wo e tth fl ct ve; i

ing' and busy, from th called line.

' furthermorebe arranged to function in response assumed to be a spacingor no current condition, the other end of the line circuit being assumedto apply a similar condition to the line. In response to the seizure ofthe repeater sta tion by a calling station .or an. operator, the polechanger applies a busy or marking condition to the toll line. After thetransmission of dialing pulses, the distant station also applies amarking or answering condition to the line circuit which consequentlywill operate the polar receiving relay at the repeating station.

After this condition has been reached, further pulses may be transmittedin either direction.

over the line circuit. For example, a rering pulse may be transmitted bythe sending station-in theform of a pulse which will cause the distantexchange to rering the called line; busy flashes maybe transmitted backto the calling line; and switchhook flashes may be transmitted in eitherdirection. 1

The polar receiving relay at the repeater station will respond toincoming pulses from the line circuit and will also respond to theanswer ing condition imposed upon the line circuit from the distant endby operating to marking position. Thus, the receiving relay is arrangedto control circuit equipment which, in well-known manner, may bearranged to respond in proper sequence to the traflic signals, such asanswer- It may to dial pulses from the distantstation, when the call isin the opposite direction, for control of the selecting operationoftelephone switches at the" exchange with which the repeater isimmediately associated.

It will, therefore, beseen that in a sense the repeater operates underfull-duplex conditions, inasmuch as it will" operate with either of twopolarities applied to either or both ends of the line circuit. However,though the repeater is required to operate in both directions, it will.

operate only in on direction at a time, so that for any particular linecondition the repeater will be operating on a half-duplex basis.

This articular condition permits out the introduction of a feature ofthe invention which basically resides in rendering the receiving relayineffective during the transmission of outgoing signals. and restoringof the receiving relay circuit to effectiveness upon termination of thetransmission of outgoing signals.

In accordance with a more specific feature of the invention, the controlcircuit from the contacts of the receiving relay is rendered immune tooperations by the receiving relay during transmission of outgoing pulsesand for this purpose by-pass circuits are provided for the receivingrelay contacts [for temporarily completing the control circuit,irrespectively of fortuitous operations by the receiving relay duringtransmission of outgoing pulses.

In accordance with another specific feature of the invention, theby-pass is applied across the marking contacts or the spacing contacts.of the relay in accordance with the position of the receiving relay atany time, as determined by the line potential applied at the distantend.

The invention will now be described more in detail as to itsorganization and operation and as applied to a specific embodiment. Inthe description reference will be made to the attached drawing, inwhich:

Figs. 1, 2 and 3 are diagrammatic representations of different typicalpulses that may be transmitted in either direction over the linecircuit; and i Fig. 4 is a circuit diagram of a repeater circuit,representing a specific application of the invention and including thefeatures of the invention. e

Referring to the drawing, it will be assumed that a subscribers stationis connected to a telephon exchange and desires to make'a call -to adistant subscribers station at another telephone exchange. The twoexchanges are connected together over toll lines.

In accordance with established traffic condi tions in the telephoneplant, the subscriber first removes his receiver from the hook,thereby'establishing a calling condition. Thereafter the subscriberoperates his calling dial which transa continuous series of busy pulseswill be transmitted back to the calling station at therate of'80impulses per minute. Other busy conditions, as for local trunks ordistant trunks, are indicated by similar pulses of differentfrequencies. Upon th distant subscriber disconnecting prematurely, arering pulse may be transemitted from the calling end of thelinecircuit. Subscribers switchhook flashes may be transmitted at anytime in either direction.

The diagram in Fig; 1 shows the signaling current in the line circuit atthe time of a call. Thus, when the line circuit is seized, the linecurrent increases from a no-current or spacing condition'to a steadymarking current condition. Thereafter the marking current is interruptedby the dialing pulses, whereupon the line current remains steady. In thecase of a subsequent rering the line current is momentarily interrupted.

Fig. 2 refers to the conditions at the called end of the toll line,which normally isapplying a spacing condition to the line circuit. Uponanswering, the called exchange transmits a steady line current which maysubsequently be interrupted by switchhook flashes.

Fig. 3 shows conditions at the called exchange when a busy conditionexists, in which case the steady marking condition is interrupted byspacing conditions.

Referring now particularly to Fig. 4, the circuit is that of a repeaterstation R connected over a toll line circuit TL to a distant exchangestation represented at E. The repeater station may be assumed to belocated at an exchange to which a plurality of subscribers areconnected, one of which is shown at S.

The subscriber station S may be a conventional station with theswitchhook 81-1 and dial -D; The station is connected over a'subscribersY limltoithe tolljzlineo'llli andcthmugh athemlowen Purposesofithetinventiomthe:line circuitwSE-Lmay 1 bevconneoted;totaltollloperator s ucircuituinsteadi 3 transfomnen fln to batterygsthessotheremiwofathei cimuittsbeing connected .torground iatithe :dial Es. The.polar nrelay: r lzillyihasrai "biasingwvindingi I-ntlnoughutheupper-:operating" wind-ingiof relay;

operating winding to the balancing network; BNLZ. fllhusnthemperationofsrelayodlllbimsending: outgoingnpulsesfl will not? ordinarilymafi'ectz the! relay 450;; 511106?) proportionatecurrents; pass;through: theatwo windings? opposing relation:

Theldistantlexohange' iE: may include a suit.-

able responsive;switchrrcontrol' circuitz'flllh. :Ihe; .;from=thecontrol circuit for relay' l'll. Relayflirli stationl E rmay also;include. a repeater circuit: sirni'lani-ito :the-scircuit It with:arreceiving relay:

similam totrelay n4 Emand: with-v transmitting, coni work :te =;ground.-Thexwindings; being opposed under--this:.: condition-,1 :relay 4.50;would mot re;-'

spond provided the balance is good. Withrrelaw 40m; anply ingrlground.to thei; duplex circuit and contacts: Mlllaat; the} distant; end of:the line coperatedutoiapplyzqhattezy, lathe; incoming; line our?rentzmillipassrthrough theupperroperating; winds ing to ground at relay(land in a ,direction:

tor-overcome: the: .ihiasin aw winding and operate relayi mnto marking;pIgf' now relay, BUFbBELOP 1 erated' toia-lso,applymbatteryl tothey-duplex aircuitgx practically no current will flow in 1 theqlineiand: through themupper. operating winding; 3 :the'; battery at relay 400will, however, send current through: the; lower operating winding 1 onrelay mm lardirection to: keep :relay 450 iopieratedxtoi marking. Thus'in receiving: incoming, marking: and spacingwpulsespthe two operating:windingss; of irelay liltwill gbe Lirrucooperatiyezrelation ntoi operateithe relay to. :markingr J01 spacing: ;re=-= spectivelyi l 1 l 3 aAlthough the receiving relay 4 is i shown: in; the drawingand isdescribed herein as "being:

connected a. differential duplexa circuititshould tie=- understood thatin accordange' with the invention; this relay may" loe+ connect'editima1 dupleiebridge cirouifiwith similar I advantages: t

amuse v linefilltoithea-repeatenstatiom QHOWGVEIQIOIWTIB? connectedthrough relay 4-301 .The1contactsmfi" this relay and thecontactswofi-relay fini and also: i

the contacts mof relay 46B are;interconnectedfito cooperate in thecontrolaof a; circuit equipment 3, Wm whicli iscgpart of. the exchangemequipment;

and 1 serves to: selectively control: switches for setting up aconnection in responseuto pulses intcomimgw rom :ai. distant exchange.to the we peater R; The equipment 410 willwhavemertainfli'pontions;represented-by airelay 4'lil, responsive v to relay- 450inraspacing. position. and: other :p'on

tions,- 1 represented by a :relay 412; responsive etc; relaw -lo'minlmarking positiom Relay ".wilL

be operateditogether; witlrre'la 4L1 2; .but znot: lot? relayi' lfllu ii l v fllhe operationtof the circuit will now lbe:d$*"

scribed: It will be assumed: that the circuit-Tie, in rest condition,.as: shown: in the 1 drawing.

"When the. "subscriber removes the: receiver i as from the hook SI-I;ground is extendedlsoyerxthew nonmallygtholding' the lrelaywin :.itsspacingxposiationtand two: operating; windings cooperating/to: f operatethe:.1relaylto.marking; The contactsiofr j relayi-eliflo are connectedthrough anizinductances subscribersl elinesL through the winding of re.-lay' lllmandmtheiprimarywof transformerr lzfl. Re lay-400appliessbattery tovthenduplex circuit and:

oyerzthez'line torthe distantzexchange for operationa Ofbthe. switchcontrol. circuit 491-.

The rise of. current through transformer 420 induces a; hshortupulse. inthe secondary winding: for temporary; operation; of relay 43in: Relay:l3Ilianormallyapplies 1 gfioundrkover itsa break contaot and over the;spacing contact of relay 450* inaccordance;withxtheabalance;hetweemthezline circuiir1TI=t1and-the.networkrBNi. i v

ton the relay Mil. When relay 43m operates it applies ground instead.over! its' make contact; and over the ibreakicontactiof relay s4 61'!torrelay' 41 :l ,cthereby excluding the contacts of relay "45.03

may orcmay not :respond to this 1 change, depending upon trafficrequirements. however; be independent of any iortuitousz= operation :by.relayr450f due uto unbalance currents: in": the. duplex; circuit causedby the operation :of relayt4'll0j. Afterwthe transition haspassed into"thezline circuitandf relay 430 has released; the: equipment lilll willagain be under controlof:

relayr llill." i I The subscriben'now operates the zdial, the: con;-tacts of which. produce spacing pulses, as i-showm in. Fig; 1, by shortinterruptions of thenground ingtheoontrol of' equipment 410:frdmtherrelay diillldurin'g' the sending of the transition :frommarkingrtospacing'. t

At; the end ofi the first dial. pulse relay" 4am operates? toi againtapply battery to" the; bridge circuitgeandi during. each pulseyseries'relay "400 i will repeat; each marking and spacing transition; During:an" interval. between pulse series? relay! 40!) remains attracted.

' either directionrto operate once vfor: each cut;

going-transition, thereby protectingtheifequipa ment 410 againstkick-off operationsflby'relay may bema'de :sluggish; enough in, its;release opterationito" rem'aint attracted during apulse ;series1onceiiit hasubeenaoperated by the first transition,

of theiseriesn The relay may, however, atthe? same time be fast enoughin releasing to release: during the interval between pulse series--andvto release aftereach transition of special super-- visony signalsof longer duration. than: the dial pulsesr l l Relays 4' will,

Relay; '43lkamay 'be' fast enough in operating:

lfini duringiany' transition; However, relay 430 has been. completed:steadyt v scriber will be rung from the ringing equipment.

at the exchange E. When the calledsubscriber answers, the conversationmay be carried on over a talking circuit, not shown in the drawing, butwhich would be closely associated with the toll line TL,.as by beingincluded in the same cable quador. by some composite arrangement.

It willnow be assumed that some special circumstance arises, as forexample, that the distant subscriber hangs up prematurely, necessi-'tating the sending of further pulses from the calling end, for example arering pulse, as indicated in Fig. 1. Relay 400 will momentarilyinterrupt the battery connection to the line and relay 630. will operatefor each transition. Underthis condition relay 530 removes the groundfrom the marking contacts of relay 456 and extends it over its makecontact and the make contact of relay 468 to the relay 4T2, therebyprotecting the relay 472 against fortuitous operation of relay 3513during each transition. Any convenient arrangement may be provided forpreventing relays E60 and 412 from releasing in response to theoperation of relay 430, as by providing make-before-break contacts onrelay In case a busy condition existed at the distant end after all dialpulses. were transmitted, a series of pulses would be transmitted by thecontacts 498 over the line TL, through the windings of relay 45B andnetwork BNto ground, causing relay Mill to operate in unison with thebusy pulses and apply corresponding busy pulses to,

the circuit Mil for suitable response. The consequent operation of relay460 will have no effect.

'. In the case of a call incoming to repeater station R, relay 85% wouldbe operated to marking in response to the application of battery at thedistant exchange E to the line. Subsequent interruptions, as by dialpulses, would cause relay fiil to oscillate and apply correspondingpulses to the circuit W8 for selective operation of switches. Inresponse to this. selective operation a switch will ultimately connectthe subscriber station S to the repeater station E. This switch isdiagrammatically represented by contacts LF; contacts LF may alsorepresent the line-finder switch for connecting the subscribers stationto the repeater in response to a call by the subscriber. With thesubscriber connected in this manner, switchhook flashes may betransmitted back to station E in the manner already described.

In case the subscriber S is busy, the connec- This will cause relays400.

' is designedso that networks of this kind may over contacts 490,through the windings of re-..

lay450, thereby operating the relay back to spacing. The circuit 410responding to this operation may be arranged to automatically disconnectthe interrupter M0 by. means of contacts 4| l,.whereupon the wholesystem will be restored to idle condition.

The inductance I is inserted between the contacts of relay 400 and theapex Pior the purpose of shaping the outgoing pulses in any desiredmanner. I

Fromthe description presented above, it will be, understood that thepurpose of relays 430 and 460 is .attained during transmission ofoutgoing pulses. Thus, in accordance with the invention andas alreadyexplained above, the balancing network is of simple construction and be.used universally with toll lines of difierent lengths and difierentcharacteristics. It is, of course, within the scope of the inventionthat-a fewstandardized types of network may be provided, each type to beused with lines having necessary, it' has been the practice to continu-:ously observe the line conditions and correspond- 1 ingly vary thebalance by the network.

In the protecting equipment shown in. the drawing the contacts of thereceiving relay are disabled during the sending of pulses,'therebypermitting the relay 450 to kick-off without disturbing effect upon theequipment 410. Thus,

an appreciable leeway is afforded in the balancing of this circuit,thereby permitting the use of universal networks for approximatebalancing over wide ranges and also 'in special cases obviating the needof continual readjustment of the network.

1 By switching the protecting circuit in accordance with the position ofthe receiving relay it is insured that fortuitous operations by thisrelay.v from either of its positions will have no disturbing eifect.

It should be understood that the invention may readily be adapted forapplication to a telegraph repeating system with similaradvantages,where sending takes place against two different signaling conditionsimposed by the remote station.

What is claimed is: l. A duplex signaling system steady stateconditions, receiving relay means at one end of said line circuit havingcontacts for,

control of a receiving circuit in response to, in-" coming marking andspacing signal pulses superimposed on said steadystate conditions,auxiliary circuit means connected to be responsive 'to out-'- goingmarking and spacingsignal pulses to pre vent said control by saidcontacts in response to unbalance currents due to said outgoing pulses.

and switching relay,means connected to bere;

sponsive to incoming line currents for the conditioning of saidauxiliary circuit means for the proper prevention of said control underboth of said steady state conditions, said auxiliary circuit meanscomprising locking circuit means connected to said contacts for lockingsaid receiving circuit in marking or spacing condition in accordancewith said conditioning; and relay means responsive to outgoing signalpulses and I vhaving normal contacts for completing said receivingcircuit during either of said steady state conditions i and havingalternate contacts for completing said locking circuit means during theoutgoing signals.

2. A duplex signaling system comprising an lap proximately balancedlinecircuit n ormal1y maintained alternately in marking and spacingsteady state conditionsfrom the remote end, receiving relay means havingcontacts for control of a receiving circuit in response to incomingmarking and spacing signal pulses superimposed on said steady stateconditions. auxiliary circuit means connected to be responsive tooutgoing marking and spacing signal pulses to prevent and switchingrelay means connected to be re! sponsive to said steady state conditionsfor the conditioning of said auxiliary circuit means for theproperprevention of saidzcontrol underboth of said steady stateconditions, said auxiliary i said receiving circuit during either ofsaid steady means during each outgoing transition, said receiving relaymeans contacts and to contacts of said pulse relay means for operationto either state conditions and having alternate contacts for momentarilycompleting said locking circuit switching relay means being connected tosaid position. 3

ROY B.

a a a J 5 said control by said contacts in response to unbalancecurrents due to said outgoing pulses,

